Electro chemical deposition systems and methods of manufacturing using the same

ABSTRACT

An electro chemical deposition system is described for forming a feature on a semiconductor wafer. The electro chemical deposition is performed by powering electrodes that includes a cathode, an anode and a plurality of electrically independent auxiliary electrodes.

This application is a divisional of U.S. patent application Ser. No.11/852,910, filed Sep. 10, 2007, which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates generally to the manufacture ofsemiconductor devices, and more particularly to electro chemicaldeposition systems and methods of manufacturing semiconductor devicesusing electro chemical deposition systems.

BACKGROUND

Semiconductor devices are used in many electronic and otherapplications. Semiconductor devices comprise integrated circuits thatare formed on semiconductor wafers by depositing many types of thinfilms of material over the semiconductor wafers, and patterning the thinfilms of material to form the integrated circuits.

Success of the semiconductor industry requires delivering higherperformance at lower cost. Consequently, maintaining production costswithin reasonable levels is one of the primary challenges insemiconductor manufacturing.

Improving product quality is another challenge in manufacturingsemiconductor devices. For example, depositing thin films involves thechallenge of maintaining a uniform deposition rate (both across waferand within wafer) along with directional deposition for filling highaspect ratio features (ratio of depth of feature to the feature's width)such as vias and trenches. As feature sizes are continually scaled alongwith wafer size, there exists a continuous need to improve filmdeposition techniques.

Deposition equipment thus needs to reduce production cost, for example,by lowering processing time (or by increasing through-put) and bylowering down time (or maintenance time), while at the same timeimproving product quality. Continued success of the semiconductorindustry requires overcoming these and other limitations.

SUMMARY OF THE INVENTION

In various embodiments, the invention describes the fabrication of anintegrated circuit using an electro chemical deposition system, theelectro chemical deposition system comprising a workpiece holderconnected to a first voltage source, a bottom electrode connected to asecond voltage source disposed below the substrate, and at least oneauxiliary electrode disposed between the bottom electrode and theworkpiece holder, the auxiliary electrode connected to at least onethird voltage source and comprising a plurality of openings.

The foregoing has outlined rather broadly features of an embodiment ofthe present invention. Additional features in various embodiments of theinvention will be described hereinafter, which form the subject of theclaims of the invention. It should be appreciated by those skilled inthe art that the conception and specific embodiment disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes for carrying out the same purposes of the presentinvention. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the spirit and scope ofthe invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 which includes FIGS. 1 a and 1 b, illustrates an embodiment ofthe invention, wherein FIG. 1 a shows a cross section of an electrochemical deposition system, and

FIG. 1 b shows a top cross section of auxiliary electrodes used in theelectro chemical deposition system;

FIG. 2, illustrates a flow diagram of one implementation in anembodiment of the invention;

FIG. 3, which includes FIGS. 3 a-3 d, illustrates an embodiment of theinvention implementing a method for deposition using an electro chemicaldeposition system;

FIG. 4, which includes FIGS. 4 a and 4 b, illustrates an embodiment ofthe invention implementing a method for deposition using an electrochemical deposition system;

FIGS. 5 a-5 c, illustrate cross sections of the auxiliary electrode ofthe electrochemical deposition system in various embodiments of theinvention, wherein the different embodiments illustrate the auxiliaryelectrode comprising a plurality of electrically independent zones;

FIGS. 6 a-6 h, illustrate top cross sections of the auxiliary electrodeof the electrochemical deposition system in various embodiments of theinvention, wherein the alternate embodiments illustrate differentgeometric features of the zones;

FIG. 7, illustrates the electrochemical deposition system in anembodiment of the invention, wherein the embodiment illustrates adifferent configuration of the auxiliary electrode;

FIG. 8, which includes FIGS. 8 a-8 e, illustrates cross sections of asemiconductor during fabrication, in accordance with embodiments of theinvention; and

FIG. 9, which includes FIGS. 9 a-9 c, illustrates the electrochemicaldeposition system in an embodiment of the invention, wherein theembodiment illustrates stacked mesh layers.

Corresponding numerals and symbols in different figures generally referto corresponding parts unless otherwise indicated. The figures are drawnto clearly illustrate the relevant aspects of the embodiments and arenot necessarily drawn to scale. To more clearly illustrate certainembodiments, a letter indicating variations of the same structure,material, or process step may follow a figure number.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of preferred embodiments are discussed in detailbelow. It should be appreciated, however, that the present inventionprovides many applicable inventive concepts that may be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use the invention,and do not limit the scope of the invention.

The invention will now be described with respect to preferredembodiments in a specific context, namely a method for formingsemiconductor structures using an electro chemical deposition process.In one embodiment, the present invention uses an auxiliary electrode inan electro chemical deposition system to improve processing time ordeposition rate without significantly reducing across wafer variation.

Electro chemical deposition systems are commonly used to deposit thinlayers of materials in semiconductor manufacturing. One of thechallenges of electro chemical deposition (ECD) systems involvesimproving deposition metrics such as deposition rates, directionality ofdeposition, uniformity of film, etc., while minimizing production costssuch as costs arising from replacement of parts and equipment downtimes. Typical ECD processes involve a compromise between the two.

In a typical electro chemical deposition system, a workpiece (wafer) tobe coated is mounted on a cathode holder in an electro chemicaldeposition chamber. A thin seed layer is deposited first over theworkpiece to enable electrical contact across the surface of the entireworkpiece, thus forming a cathode on the workpiece. The chamber furthercontains an electrolyte disposed over an anode. The workpiece isimmersed into an electrolyte that comprises metallic ions to bedeposited. The electrolyte is continuously circulated into the electrochemical deposition chamber. A potential difference is developed acrossthe chamber by biasing or powering the anode and cathode. The potentialdifference drives the metal ions to the cathode and starts anelectrochemical deposition at the cathode, as per the electrochemicalreaction: M^(n+)+ne⁻→M. The reaction denotes the formation of metal M onthe surface of the wafer, by reducing the charged metallic ion M^(n+)with electrons from the cathode and the electrolyte.

The deposition rate on a flat substrate, for example, given by theVolmer-Butler equation, is proportional to the concentration of themetal ions at the cathode/electrolyte interface, the equilibrium currentat the cathode (or exchange current), and the overpotential (potentialdifference between the electrodes). The exchange current defines the netrate of deposition in the absence of an external electric potential, andprimarily depends on the system (electrolyte, metal being deposited,etc.). Further, in a typical ECD system, additives and inhibitors areadded for filling high aspect ratio features. The additives, such asaccelerators and inhibitors, selectively adsorb on the top surfaces andcontrol the number of available sites for deposition. The concentrationof the metal ions at the cathode/electrolyte interface depends on thediffusion and field driven drift of the metal ions from the bulkelectrolyte to the cathode/electrolyte interface. Modern ECD systemsinclude a flow regulator or a diffuser to control the concentration ofthe metal ions flowing into the cathode/electrolyte interface. However,changes in the electric potential still play the critical parameter incontrolling the deposition rate. The electric potential changes theelectro chemical reaction by changing the net free energy of thereaction. Hence, changes in the electric potential result in anexponential change in the deposition rate.

The workpiece contacts the cathode around the corners or outer regionsof the workpiece. Consequently, the electric potential in the innerregions of the workpiece may be reduced due to ohmic loss arising fromresistance of the conductive path. The resistance of the conductive pathdepends on the lowest resistive path from the outer electricallycontacted regions to the inner regions. Before the start of the electrochemical deposition process, the seed layer forms this conductive path.The resistance of the seed layer depends inversely on the thickness ofthe seed layer. Consequently, in deeply scaled technologies, as thethickness of the seed layer decreased to fill high aspect ratiofeatures, the resistance of the seed layer increases. This increasedseed layer resistance manifests as a larger potential drop from theouter regions to the inner regions of the workpiece. Hence, inconventional ECD systems, the deposition rate of copper is non-uniform,resulting in a non-uniform across wafer deposition. Such non-uniformfilling may result in increased production costs due to poor acrosswafer yield. Similarly, redesign of the equipment to overcome theselimitations can be expensive.

Hence, methods that simultaneously improve film deposition andproduction costs without compromising deposition quality or yield areneeded.

In preferred embodiments, the present invention discloses the use ofauxiliary electrodes in electro chemical deposition systems forenhancing film deposition and/or decreasing production costs. In aparticular embodiment, the auxiliary electrodes may be used to increasethe deposition rate uniformity of the ECD process. For example, theauxiliary electrode may increase the electrode over potential (orpotential drop) in regions selectively, and thus increase depositionrate.

Although explained in a particular embodiment, as will be evident,concepts of the invention can be applied, to other techniques. Forexample, the invention is applicable to other applications that useelectro-deposition such as corrosion resistance, as well as depositionsusing electro-less plating.

An embodiment of the invention is illustrated in FIG. 1 and variousembodiments using these concepts will then be described using FIGS. 3-7and the electro chemical deposition systems of FIG. 7. FIG. 8illustrates the use of embodiments of the invention in fabricating asemiconductor device.

FIG. 1, which includes FIGS. 1 a and 1 b, illustrates an embodiment ofthe invention, wherein FIG. 1 a shows a cross section of an electrochemical deposition system, and FIG. 1 b shows a top cross section ofthe electro chemical deposition system.

Referring to FIG. 1 a, the electro chemical deposition system isdisposed in a chamber 11 and comprises a workpiece holder 12 connectedto a first potential source 12 v, an anode 15 connected to a secondpotential source 15 v, a plurality of auxiliary electrodes 30 disposedbetween the workpiece holder 12 and the anode 15. Each of the auxiliaryelectrodes 30 comprises independent electrical zones 25-27, the zonesconnected to an independent potential 25 v-27 v. A wafer or workpiece 14may be mounted on the workpiece holder 12. The workpiece 14 is mountedon the corners of the wafer and avoids damaging sensitive regions of thewafer. The electro chemical deposition system further comprises anelectrolyte 18 flowing in through an inlet 22 and flowing out throughoutlet 23. The electrolyte flows into a diffuser 29 disposed above theanode 15. The metal is deposited by an application of a suitablepotential to the workpiece holder 12, anode 15 and auxiliary electrode30. All the electrodes comprising the workpiece 12, anode 15 andauxiliary electrodes 30 are connected to a main control unit 31.

The metal to be deposited may comprise copper, gold, silver, chromium,rhodium, nickel, zinc, etc. The electrolyte typically comprises a metalto be deposited and may comprise copper, gold, silver, chromium,rhodium, nickel, zinc, etc. In some embodiments, the deposited metal maybe an alloy comprising a combination of metals. The electrolytepreferably is a compound dissolved in a solution. For example, fordepositing copper, a copper sulphate may be deposited in water.

The electrolyte performs a number of functions besides being a source ofthe metal or metals. For example, the electrolyte may comprisecomponents that form complexes with ions of the deposition metal,maintain a suitable conductivity, stabilize the solution against, forexample, hydrolysis, work as a buffer and stabilize the pH, regulate thephysical form of the deposit, for example, maintain super-fill effectwhen filling vias of different configurations, aid in dissolving theanode 15, as well as suitably modify other properties, either of thesolution or of the deposit.

The anode 15 may replenish the depleting electrolyte and hence be aconsumable anode 15 or it may be inert. The anode 15 may comprisecopper, gold, silver, platinum, tungsten, and combinations thereof.

The diffuser 29 enables a uniform flow of electrolyte to the surface ofthe workpiece 14. Hence, in a limited way the diffuser 29 can helpminimize, for example, variations across wafer. The diffuser may bedesigned to control both the electrolyte 18 flow as well as the electricfield lines which determine the potential drop between the anode 15 andthe workpiece 14.

FIG. 1 b, illustrates the independent electrical zones 25-27 in a topcross sectional view of the auxiliary electrode 30. Each electrical zone25-27 may comprise a suitable structure and may create a uniformelectric field around the zone.

The auxiliary electrode 30 in preferred embodiments comprises the samematerials as the anode 15. However, in some embodiments, the auxiliaryelectrode 30 comprises other materials. For example, in someembodiments, the auxiliary electrode 30 may be made of a consumableelectrode, whereas the bottom electrode may not be consumable. Such adesign may be advantageous to avoid expensive replacement of the bottomelectrode, while using the auxiliary electrode 30 to partially replenishthe electrolyte during deposition. The auxiliary electrode 30 in variousembodiments comprises copper, gold, silver, platinum, tungsten, andcombinations thereof.

In preferred embodiments, the auxiliary electrodes 30 are designed tominimize resistance to the flow of the electrolyte 18. However, in someembodiments, the auxiliary electrodes 30 may also be used as a flowregulator to control the flow of the electrolyte across the surface ofthe workpiece 14. Even though, the auxiliary electrode 30 is disposedover the diffuser 29 in the preferred embodiment, in variousembodiments, the auxiliary electrode 30 may also be attached to thediffuser 29. In some embodiments, the auxiliary electrode 30 may also belocated in a different location in the chamber 11. In variousembodiments, for a particular product, the auxiliary electrodes 30 maybe altered to maximize, for example, product yield. The use of separateauxiliary electrodes 30 allows easy redesign of the potential on theworkpiece 14 without expensive redesigns.

An embodiment of the invention for a method of manufacturingsemiconductor devices will now be described using FIGS. 2 and 3. Thecurrent method describes the electrochemical deposition process forforming. For example, copper metal lines and vias used in manufacturingintegrated circuits. The flow chart of FIG. 2 will be described usingFIG. 3. In particular, FIG. 3 a shows different zones on the surface ofa wafer or workpiece 14, and FIG. 3 b illustrates the formation of filmusing the ECD process in the absence of auxiliary electrodes, resultingin non-uniform film deposition. FIG. 3 d illustrates overcoming thelimitations shown in FIG. 3 b, resulting in a tunable film thicknessacross multiple zones of the wafer, using the auxiliary electrode shownin FIG. 3 c.

As shown in FIG. 2, box 1001, the wafer or workpiece is divided into anumber of zones. The zones are preferably divided in a concentric manneralthough in some embodiments, the zones may not be concentric. This isshown in FIG. 3 a, which refers to the workpiece 14 comprising zones 60and 61. Zones 60 and 61 are coated with a seed layer for subsequentelectrochemical deposition. Zones 60 and 61 could be any zone on thesurface of the workpiece 14. In various embodiments, these could becontrol structures or dummy structures intentionally added into theproduct design for controlling the ECD process.

For clarity, FIG. 3 b, illustrates film growth in the absence of theauxiliary electrodes. As shown in FIG. 3 c, zones 60 and 61 havedifferent cathode potentials (potential on the workpiece) at a starttime (t=0). In particular, the zone 61 represented by curve 61 c has acathode potential V₀(61) at t=0, whereas the zone 60 represented bycurve 60 c has a cathode potential V₀(60) at t=0. The difference incathode potential (V₀(60)-V₀(61)) between the zones 60 and 61 arisesfrom a difference in resistance between the node 12 v of FIG. 1 a andthe respective region. The resistance of the film is reduced as the filmincreases in thickness. Hence, the cathode potential increases. If noadditional auxiliary electrode 30 potential is applied, the grown film(film thickness after end time t_(f)) in such a scenario maps thedifference in the initial potential. Hence, after completion of theelectrochemical deposition, the film in zone 60 (shown by curve 600 isthicker than the film in zone 61 (shown by curve 610. This non-uniformfilm thickness can be deleteriously magnified during subsequentprocessing, for example, during planarization steps (e.g., copper CMP)and may result in across wafer yield loss.

As shown in box 1002 of FIG. 2, the auxiliary electrode 30 is tailoredor programmed for a specific product design. In the embodiment shown inFIG. 3 c, the auxiliary electrode 30 comprises zones 60 and 61 connectedto independent voltage sources 60 v and 61 v respectively. In otherembodiments, generic designs for the auxiliary electrode 30 (as will bediscussed in later embodiments) may also be used. In variousembodiments, these generic auxiliary electrodes may be programmed at thebeginning of an ECD process run for processing a number of waferscomprising similar product designs.

FIG. 3 d, along with the flowchart of FIG. 2 (boxes 1003-1009),illustrates an embodiment of the invention, wherein the auxiliaryelectrode 30 is biased based on a criterion. As shown in box 1001 ofFIG. 2, the wafer is divided into a plurality of zones or regionscorresponding to the zones on the auxiliary electrode. The thickness ofthe film in each zone is measured at the start time (t=0). At the startof the process, this is typically the seed layer thickness. Thethickness may be calculated either optically using techniques such asellipsometry or electrically using the current flow in the auxiliaryelectrodes 30. Based on the thickness of the seed layer, a workpiecepotential for each zone is calculated. The zones in the auxiliaryelectrode 30 are biased, for example, to match the electrochemicalpotential difference PD(61) and PD(60) between the cathode and the anodein the zones 60 and 61. The measured film thickness in each zone alongwith a target film thickness is used to calculate a target growth ratefor each zone. The potential of the auxiliary electrodes in each zone isadjusted to enable deposition at the target growth rate. After a certaintime, the above steps (measurement, calculation of target growth rateand cathode potential, biasing of auxiliary electrode) may be repeatedtill the final thickness is achieved. In FIG. 3 d, the time evolution ofthe above steps for zones 60 and 61 is shown for the cathode potentialV(60) and V(61), the auxiliary potential (A(60) and A(61)) (shown inFIG. 4 a) and the potential difference PD(60) and PD(61).

As will be illustrated in various embodiments in FIGS. 4 a and 4 b, thefilm thickness in any zone may be tailored to meet a target requirement.For example, the target film thickness may be non-uniform to account fornon-uniformity of subsequent processes. In one particular example, theplanarization step following electrochemical deposition typically thinswafer edges faster than the wafer center. Hence, the electrochemicaldeposition may be tailored to deposit a thinner film in the center and athicker film towards the edge of the wafer.

FIG. 4 a, illustrates an embodiment in which the target film thicknessin zone 60 of workpiece 14 is larger than the target film thickness inzone 61 of workpiece 14. However, in the embodiment shown in FIG. 4 a,at start time, the workpiece potential of zone 60 is higher than theworkpiece potential of zone 61. Hence, using the flowchart of FIG. 2, aconstant potential is applied in the zones 60 and 61. As the potentialon zone 61 is larger than the potential on zone 60, the film thicknessin zone 60 is larger than the film thickness in zone 61. The largerpotential of the auxiliary electrodes 30 in the zone 61 compensates forits lower cathode potential.

FIG. 4 b, illustrates an embodiment in which the target film thicknessin zone 60 is the same as the target film thickness in zone 61. However,in the embodiment shown in FIG. 4 b, at start time, the workpiecepotential of zone 60 is higher than the workpiece potential of zone 61.Hence, using the flowchart of FIG. 2, the potential applied in the zones60 and 61 is varied until a similar film thickness is obtained. As thepotential on zone 61 is larger than the potential on zone 60, at thebeginning the film thickness in zone 60 is larger than the filmthickness in zone 61. However, as the film thickness increases, thepotential drop between the two zones reduces, and hence the potential ofthe auxiliary electrode on zone 61 may be progressively reduced.

Embodiments of the invention illustrating the auxiliary electrode willnow be described using FIG. 5, which includes FIGS. 5 a and 5 b, showingtop cross-sectional views of the auxiliary electrode and FIG. 5 c whichillustrates a cylindrical plate auxiliary electrode.

Referring now to FIG. 5 a, the auxiliary electrode 30 comprises a numberof electrically independent zones 100-109, 111-119, and 121-129. Theelectrically independent zones are separated by a suitable insulator110. Each zone may be biased by an independent electrical source (notshown). The electrically independent zones 100-109, 111-119, and 121-129are positioned in concentric zones and separated axially. Although inthe described embodiment only four concentric layers are illustrated,more or fewer concentric zones may be formed in various embodiments.

Referring now to FIG. 5 b, the auxiliary electrode 30 compriseselectrically independent zones 210-258 separated by a suitable insulator110. Each zone may be biased by an independent electrical source (notshown). The electrically independent zones 210-258 are positioned inconcentric zones 201-206. Although in the described embodiment only sixconcentric layers are illustrated, more or fewer concentric zones may beformed in various embodiments. The auxiliary electrode 30 is separatedaxially into 8 zones, although in other embodiments more or fewer axialzones may be present.

FIG. 5 c, illustrates an embodiment wherein the auxiliary electrode 30is formed as a cylindrical plate. For example, in FIG. 5 c, theelectrical independent zones 311-313 form the auxiliary electrode 30.

In various embodiments, the auxiliary electrodes 30 may comprise stackedmesh layers or stacked layers (FIG. 9 a). In some embodiments, thenumber of such mesh layers may vary across the auxiliary electrodes 30(FIG. 9 b). For example, the central regions of the auxiliary electrodes30 may comprise more mesh layers than the edges of the auxiliaryelectrodes 30. Similarly, different layers of the auxiliary electrodes30 may be staggered (FIG. 9 c).

Embodiments of the invention illustrating the zones comprising theauxiliary electrodes 30 will now be described using FIG. 6. As shown inFIG. 6, which comprises FIGS. 6 a-6 h, each zone may comprise any shapeor pattern. In a preferred embodiment, the shape and pattern areselected to minimize any hindrance to the flow of electrolyte throughthe auxiliary electrode. Hence, the zones in the auxiliary electrodes 30have a mesh or grid shape as illustrated in the various embodiments ofFIG. 6. In different embodiments, the mesh comprises a network ofconnectors. The connector may comprise suitable curve elements ofvarying widths and spacings. For example, the mesh pattern may be asquare (FIG. 6 a), a triangle (FIG. 6 b), a trapezoid (FIG. 6 c), arhombus (FIG. 6 d), an ellipse (FIG. 6 e), a concave surface (FIG. 6 f),a convex surface (FIG. 6 g), or a spiral (FIG. 6 h). Similarly, the meshmay comprise combinations of one or more of these embodiments. Althoughnot shown, the mesh may comprise any suitable shape in variousembodiments.

An embodiment of the electrochemical deposition system is shown in FIG.7. FIG. 7 shows a workpiece holder holding a workpiece 14 disposed abovethe anode 15. The auxiliary electrodes 30 are positioned between theanode 15 and the workpiece 14. However, the distance from the auxiliaryelectrodes 30 to the workpiece 14 can be modified by changing, forexample, the geometry of the auxiliary electrodes 30. For example, inFIG. 7, the auxiliary electrodes 30 are modified such that the center iscloser than the edges. Hence, the effectiveness of the auxiliaryelectrode 30 increases due to increased penetration of the electricfield lines from the auxiliary electrode 30. In other words, thepotential drop across the electrolyte varies, about linearly, as afunction of the thickness of the electrolyte. Using this embodiment, asingle potential source may be used to modulate the potential on theworkpiece 14. In different embodiments, this variation in geometry maybe combined with multiple zones to have an optimized control of thecathode potential across the workpiece 14.

Embodiments of the invention may be applied to minimize variationscaused by changes in pattern density. A typical wafer comprises a numberof zones of varying pattern density. The presence of dense patterns (forexample, vias) increases the resistance, and hence potential drops inzones locally around these dense patterns. Embodiments of the methodsdescribed herein may be suitably adopted to incorporate such locationvariations in resistance.

An embodiment of the invention describes a method using theelectrochemical deposition system to fabricate a semiconductor device600. A sequence of process steps used in the formation of thesemiconductor device 600 will now be described.

As illustrated in FIG. 8 a, the device 600 first goes through front endprocessing that includes formation of all the active componentsincluding gate stack 26, STIs 38, source/drain zones 54 and 56, andsilicide zones 58. After forming the front end components, the device600 undergoes back end of the line manufacturing, wherein contacts aremade to the semiconductor body and interconnected using metal lines andvias. Modern integrated circuits incorporate many layers of verticallystacked metal lines and vias (multilevel metallization) thatinterconnect the various components in the chip.

Referring now to FIG. 8 b, a first insulating material layer 114 is thenformed over a etch stop liner 112. The etch stop liner 112 is depositedover the semiconductor body. For example, a nitride film (e.g., siliconnitride) is deposited. The first insulating material layer 114preferably comprises insulating materials typically used insemiconductor manufacturing for inter-level dielectric (ILD) layers,such as SiO₂, tetra ethyl oxysilane (TEOS), fluorinated TEOS (FTEOS),doped glass (BPSG, PSG, BSG), organo silicate glass (OSG), fluorinatedsilicate glass (FSG), spin-on glass (SOG), SiN, SiON, low k insulatingmaterials, e.g., having a dielectric constant of about 4 or less, orcombinations or multiple layers thereof, as examples, althoughalternatively, the first insulating material layer 114 may compriseother materials. The ILD layer may also comprise dense SiCOH or a porousdielectric having a k value of about 3 or lower, as examples. The ILDlayer may also comprise an ultra-low k (ULK) material having a k valueof about 2.3 or lower, for example. The ILD layer may comprise athickness of about 500 nm or less, for example, although, alternatively,the ILD layer may comprise other dimensions.

As illustrated in FIG. 8 b, in zones where the contact is to be made,the first insulating material layer 114 is etched down to the etch stopliner 112. In one exemplary process, photoresist (not shown) isdeposited and patterned to mask off the non-exposed zones to the etch.The first insulating material layer 114 is then etched down to the etchstop liner 112 using standard etch techniques such as a reactive ionetch. In this step, the first insulating material layer 114 etches awayat a faster rate than the etch stop liner 112. Once the etch iscomplete, the photoresist may be removed. Contact holes are formed by asecond etch. This time, the etch stop liner 112 is etched to expose thesilicide zones 58 using the first insulating material layer 114 as amask.

As illustrated in FIG. 8 b, a first conductive liner 115, may bedeposited prior to filling the contact hole with a first conductivematerial. The first conductive liner 115 is preferably conformal, andmay comprise a single layer of Ta, TaN, WN, WSi, TiN, Ru andcombinations thereof, as examples. The first conductive liner 115 istypically used as a barrier layer for preventing metal from diffusinginto the underlying semiconductor and first insulating material layer114 material. These liners are deposited, for example, using a chemicalvapor deposition (CVD), plasma vapor deposition (PVD) or Atomic layerDeposition (ALD) process.

As illustrated in FIG. 8 c, a first conductive material 116 is thendeposited similarly using, for example, a CVD, PVD or ALD process overthe first insulating material layer 114 and the first conductive liner115 to fill the contact hole. Excess portions of the first conductivematerial 116 are removed from the top surface of the first insulatingmaterial layer 114, e.g., using a chemical-mechanical polishing (CMP)process forming at least one contact plug or via 117.

The first conductive material 116 preferably comprises tungsten,although copper, aluminum, Al—Cu—Si, other metals and combinationsthereof may also be used. If the first conductive material 116 comprisestungsten, preferably a bi-layer seed layer comprising CVD titaniumnitride and silicon doped tungsten are used. In some embodiments, thecontact plug 117 is filled with copper, foregoing the titanium nitrideliner (first conductive liner 115) which may be problematic in deeplyscaled technologies.

Referring now to FIG. 8 d, a second insulating layer 118 is depositedover the first insulating layer 114. The second insulating layer 118preferably comprises a low-k dielectric material having a dielectricconstant of 3.6 or less, and may require heating, e.g., up to 400° C. toremove solvents. The second insulating layer 118 is patterned vialithography, e.g., with a mask. A photoresist is deposited over thesecond insulating layer 118, and portions of the photoresist areexposed, developed and removed, leaving a pattern for a metal line. Theexposed second insulating layer 118 is removed to form openings in thesecond insulating layer 118.

A second conductive liner 136 is preferably deposited using a conformaldeposition process, leaving a conformal liner or diffusion barrier 136along the interior walls of the openings. Preferably the secondconductive liner 136 comprises tantalum nitride deposited by plasmavapor deposition (PVD). Alternatively, the second conductive liner 136may comprise titanium nitride, tungsten nitride, a refractory metal orother barrier layers that may be conformally deposited, for example,using CVD, PVD processes or electro-less plating. The second conductiveliner 136 may comprise a bi-layer of material, including, for example, abarrier layer and a conformal seed layer, which preferably comprisecopper, aluminum, other metals or combinations thereof. The seed layermay be deposited using a CVD or a PVD process, for example.

The remainder of the openings is filled with second conductive material138, for example, using an embodiment of the invention of theelectrochemical deposition process. As shown in FIG. 8 e, theelectrochemical deposition process creates a first metal line (ML1)having a portion residing within the second insulating layer 118 and aportion residing over the first insulating layer 114. The first metalline (ML1) includes a source metal line 139, a drain metal line 141 anda gate metal line 140. The second conductive material 138 preferablycomprises copper, although it may comprise other metals such as gold,silver, and aluminum in other embodiments.

The electrochemical deposition process may be performed by biasing theanode 15 of FIG. 1 a, the workpiece holder 12 of FIG. 1 a, and theauxiliary electrode 30 of FIG. 1 a using the embodiments described by,for example, the flow chart shown in FIG. 2. In preferred embodiments,the potential on the auxiliary electrode is less than the potential onthe anode, although in other embodiments, they may be unrelated. Thedimension (parallel to the surface of the workpiece) of the auxiliaryelectrode is similar to the dimension of the workpiece, although inother embodiments it may comprise other suitable dimensions.

The second conductive material 138 may be filled using either a singleor multiple damascene process. In a single damascene process, a singlelayer of insulating material is patterned with a pattern for conductivefeatures, such as conductive lines, conductive vias, or contacts, forexample. In contrast, in a dual damascene process, the vias and metalslines are patterned for conductive features and filled in a single fillstep with a conductive material. Although preferred embodiments use adouble damascene process, embodiments of the present invention may alsobe formed in single or multiple damascene processes. In a multipledamascene process, three or more insulating material layers arepatterned with patterns for conductive features and are later filled ina single fill step with a conductive material. Damascene processes aretypically used when the conductive line material comprises copper, forexample.

A third dielectric layer 122 may be deposited over the second dielectriclayer 118 and first metal line 138 to form the first via level V1. Forexample, the third dielectric layer 122 may be patterned and etched tocreate via holes or openings. The via holes may be filled with aconductive liner 131 and a seed layer (not shown), followed byelectroplating a conductive material, such as copper, to form vias 149,150 and 151. The device at this stage is shown in FIG. 8 e.

Further processing completes the formation of the semiconductor device600. For example, further levels of metal lines and vias (metallization)ML2, V2, ML3, V3, ML4, V4, etc. (not shown) could proceed as discussedabove by repeating the process for formation of metal lines 139-141, andvias 149-151. In some embodiments, the dimensions of the higher metallevels may be increased to reduce resistance of the metal lines.

It will be readily understood by those skilled in the art that materialsand methods may be varied while remaining within the scope of thepresent invention. It is also appreciated that the present inventionprovides many applicable inventive concepts other than the specificcontexts used to illustrate preferred embodiments. Accordingly, theappended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. An electro chemical deposition system comprising:a workpiece holder disposed in an electro chemical deposition chamberand connected to a first voltage source; a bottom electrode disposedbelow the workpiece holder with the electro chemical deposition chamber,wherein the bottom electrode is connected to a second voltage source; atleast one auxiliary electrode disposed in the electro chemicaldeposition chamber and comprising a plurality of openings disposedbetween the bottom electrode and the workpiece holder, wherein theauxiliary electrode is connected to at least one third voltage source,wherein the at least one auxiliary electrode has a convex shape suchthat a first nearest distance is less than a second nearest distance anda third nearest distance is more than a fourth nearest distance, whereinthe first nearest distance is the nearest distance from a center portionof the at least one auxiliary electrode to the workpiece holder, whereinthe second nearest distance is the nearest distance from an edge portionof the at least one auxiliary electrode to the workpiece holder, whereinthe third nearest distance is the nearest distance from the centerportion of the at least one auxiliary electrode to the bottom electrode,and wherein the fourth nearest distance is the nearest distance from theedge portion of the at least one auxiliary electrode to the bottomelectrode; and a diffuser disposed between the workpiece holder and thebottom electrode, the diffuser configured to control electric fieldlines in the electro chemical deposition chamber, wherein the diffuseris separated physically from the at least one auxiliary electrode. 2.The electro chemical deposition system of claim 1, wherein a workpieceis mounted on the workpiece holder and is in electrical contact with theworkpiece holder.
 3. The electro chemical deposition system of claim 1,further comprising an electrolyte disposed between the workpiece holderand the bottom electrode, wherein the electrolyte flows through the atleast one auxiliary electrode, and wherein the diffuser is configured tocontrol a flow of an electrolyte.
 4. The electro chemical depositionsystem of claim 1, wherein the bottom electrode and the at least oneauxiliary electrode comprise materials of different composition.
 5. Theelectro chemical deposition system of claim 1, wherein the bottomelectrode comprises a material selected from the group consisting ofcopper, gold, silver, chromium, rhodium, nickel, zinc, and combinationsthereof.
 6. The electro chemical deposition system of claim 1, whereinthe at least one auxiliary electrode comprises a material selected fromthe group consisting of copper, gold, silver, chromium, rhodium, nickel,zinc, and combinations thereof.
 7. The electro chemical depositionsystem of claim 1, wherein the at least one auxiliary electrodecomprises a plurality of electrically independent zones, and whereineach zone is independently connected to a different voltage source. 8.The electro chemical deposition system of claim 1, wherein the at leastone auxiliary electrode comprises a mesh, wherein the mesh furthercomprises a network of connectors, and wherein each connector comprisesa curve element.
 9. The electro chemical deposition system of claim 8,wherein the curve elements have a plurality of widths.
 10. The electrochemical deposition system of claim 8, wherein distances between theconnectors are different within the mesh.
 11. The electro chemicaldeposition system of claim 8, wherein the at least one auxiliaryelectrode comprises stacked mesh layers.
 12. The electro chemicaldeposition system of claim 11, wherein a number of mesh layers in thestacked mesh layer varies across the at least one auxiliary electrode.13. The electro chemical deposition system of claim 11, wherein thestacked mesh layers of the auxiliary electrode are staggered betweeneach layer.
 14. The electro chemical deposition system of claim 1,wherein the at least one third voltage source provided a differentvoltage than the first and the second voltage sources.
 15. An electrochemical deposition system comprising: a workpiece holder disposed in anelectro chemical deposition chamber and connected to a first voltagesource; a bottom electrode disposed below the workpiece holder with theelectro chemical deposition chamber, wherein the bottom electrode isconnected to a second voltage source; at least one auxiliary electrodedisposed in the electro chemical deposition chamber and comprising aplurality of openings disposed between the bottom electrode and theworkpiece holder, wherein the auxiliary electrode is connected to atleast one third voltage source, wherein the at least one auxiliaryelectrode has a convex shape such that a first nearest distance is lessthan a second nearest distance and a third nearest distance is more thana fourth nearest distance, wherein the first nearest distance is thenearest distance from a center portion of the at least one auxiliaryelectrode to the workpiece holder, wherein the second nearest distanceis the nearest distance from an edge portion of the at least oneauxiliary electrode to the workpiece holder, wherein the third nearestdistance is the nearest distance from the center portion of the at leastone auxiliary electrode to the bottom electrode, and wherein the fourthnearest distance is the nearest distance from the edge portion of the atleast one auxiliary electrode to the bottom electrode; and anelectrolyte disposed between the workpiece holder and the bottomelectrode, wherein the electrolyte flows through the at least oneauxiliary electrode.
 16. The electro chemical deposition system of claim15, further comprising a diffuser disposed between the workpiece holderand the bottom electrode, the diffuser configured to control electricfield lines in the electro chemical deposition chamber, wherein thediffuser is separated physically from the at least one auxiliaryelectrode, and wherein the diffuser is configured to control a flow ofan electrolyte.
 17. The electro chemical deposition system of claim 15,wherein the at least one auxiliary electrode comprises a plurality ofelectrically independent zones, and wherein each zone is independentlyconnected to a different voltage source.
 18. The electro chemicaldeposition system of claim 15, wherein the at least one auxiliaryelectrode comprises a mesh, wherein the mesh further comprises a networkof connectors, and wherein each connector comprises a curve element. 19.The electro chemical deposition system of claim 18, wherein distancesbetween the connectors are different within the mesh.
 20. The electrochemical deposition system of claim 18, wherein the at least oneauxiliary electrode comprises stacked mesh layers.
 21. The electrochemical deposition system of claim 20, wherein a number of mesh layersin the stacked mesh layer varies across the at least one auxiliaryelectrode.
 22. The electro chemical deposition system of claim 20,wherein the stacked mesh layers of the auxiliary electrode are staggeredbetween each layer.
 23. The electro chemical deposition system of claim15, wherein the at least one third voltage source provided a differentvoltage than the first and the second voltage sources.
 24. An electrochemical deposition system comprising: a workpiece holder disposed in anelectro chemical deposition chamber and connected to a first voltagesource; a bottom electrode disposed below the workpiece holder with theelectro chemical deposition chamber, wherein the bottom electrode isconnected to a second voltage source; and at least one auxiliaryelectrode disposed in the electro chemical deposition chamber andcomprising a plurality of openings disposed between the bottom electrodeand the workpiece holder, wherein the auxiliary electrode is connectedto at least one third voltage source, wherein the at least one auxiliaryelectrode has a convex shape such that a first nearest distance is lessthan a second nearest distance and a third nearest distance is more thana fourth nearest distance, wherein the first nearest distance is thenearest distance from a center portion of the at least one auxiliaryelectrode to the workpiece holder, wherein the second nearest distanceis the nearest distance from an edge portion of the at least oneauxiliary electrode to the workpiece holder, wherein the third nearestdistance is the nearest distance from the center portion of the at leastone auxiliary electrode to the bottom electrode, and wherein the fourthnearest distance is the nearest distance from the edge portion of the atleast one auxiliary electrode to the bottom electrode.
 25. The electrochemical deposition system of claim 24, wherein the at least oneauxiliary electrode comprises stacked mesh layers.
 26. The electrochemical deposition system of claim 24, wherein the at least oneauxiliary electrode comprises a plurality of electrically independentzones, and wherein each zone is independently connected to a differentvoltage source.
 27. The electro chemical deposition system of claim 24,wherein the at least one third voltage source provided a differentvoltage than the first and the second voltage sources.